Need minimalistic example to get STM32 in 48 - pin Package to work.

Forum|Forum|8 years ago
November 27, 2017
4 replies
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Posted on November 27, 2017 at 13:47

I can't get a STM32 in 48 - pin Package to work. I need a minimal working reference.

I have a STM32F042K6T6, It works fine, no problems, when I am using it on a breakout board:

Reset pin voltage goes to VDD level, Debugger works, I have a firmware project with Display, External ADC, etc, everything works.

It is LQFP 32. I need more I/O's, so I decided to switch to a 48 pin device.

I picked an STM32L443CCT6 for that, and also because I want the FPU of the M4 and the low power features.

So this is a breakout board I prepared for that:

Problem is: I can't get it up and running.

I tried several times with different types of 64 pin STM32 devices.

The Reset pin voltage stays at VSS level.

I connected it as follows:

pin 7: 100 nF cap to GND (reset pin)

pin 8, 23, 35 and 47: GND

pin 9, 24, 48: VDD = 3V3

pin 44: 10 K resistor to GND (BOOT0 pin)

I also added a 10 uF cap between pin 23 and 24, and two 100nF caps between pins 8/9 and 47/48 (soldered on the bottom side)

Can anyone help ?

Maybe provide a working minimalistic connection exaple for a 48 pin STM32, if possible for the L443CCT6 ?

Maybe the problem is something else, maybe because it is a fresh device and the system clocks are not set correctly ?

Or does anyone know a better breakout board or a minimalistic reference board other than nucleo, i.e. no extra components ?

Or anything else maybe.

BTW I use an ST-link V2 with 4 wire: GND, VDD, SWDIO and SWCLK connected. On the STM32F042K6T6 is works fine, no problems.

I also have nucleo boards with F042K6T6 and L452RET6. None of them, howwever, use a 48 pin device.

#stm32-l4 #lqfp48

STM32L4 series

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Uwe Bonnes

Chief

Posted on November 27, 2017 at 14:46

'It does not work' is a very generic and not very helpfull statement. One possible cause could be your missunderstanding about decoupling capacitors. Decoupling capacitors do not need to be places somewehere, but places close to the device. Take your finger, start at the center og the chip, then follow VCC out to your capacitor and back over to VCC back to the chip. If the loop is 'to large', problems may arise as decpupling will not work sufficent. Another problem is with missing ground 'plane ' on your board. They only connect off board. That may also cause problem.

Oliver R.Author

Associate II

Posted on November 27, 2017 at 17:08

'It does not work' -> The reset pin level stays at VSS level. That indicates that the CPU is not running. If the CPU runs, the level on that pin rises to VDD. Sorry if I wasn't clear enough with that.

Decoupling capcitors: I did place them as close as possible, between pin 23/24, 8/9 and 47/48, which are all VDD/VSS pairs. The other device (STM32F042K6T6), in contrast, works fine, even without decoupling caps and no ground plane.

It would help If someone could provide a tested reference design or anything as reference that works, whichI could easily build as prototype.

I know the nucleo boards or for example the pyboard could be a reference, but then I must make a PCB, which I will do later, but that still wouldn't explain to me why the breakout board doesn't work.